Electrical heating apparatus



May 9, 1944. H. c. GILLESPIE ELECTRICAL HEATING APPARATUS Filed Feb. 2;1942 UmSQh- Ema QR Enventor Henderson C. Gillespie (Ittomeg Patented May9,

ELECTRICAL HEATING APPARATUS Henderson 0. Gillespie, Moorestown, N. 1.,assignor to Radio Corporation of America, a corporation of DelawareApplication February 2, 1942, Serial No. 429,276

. 6 Claims.

This invention relates to a heating device, and .more particularly to adevice. for heating conductive articles by induction from a source ofelectrical en of high frequency, the present invention being directed tothe type of heating device disclosed in my 'copending application SerialNo. 420,956, filed November 29, 1941, now Patent No. 2,314,875, grantedMarch 30, 1943, and being particularly directed to the control means forcontrolling the supply of energy from the high frequency energy sourceto the coupling coil.

In the aforesaid patent, there is disclosed a heating device adapted forlocal rapid heating in many industrial applications. This devicecomprises a single-turn coupling coil which is coupled to a highfrequency oscillator through a step-down transformer, the coupling coilproviding a high, concentrated magnetic field which induces eddycurrents in a conductive article which is to be heated. Since thewindings of the transformer and the coupling coil become quite hot,suitable aspirator means involving a stream of compressed air isemployed to draw cooling air over the transformer windings, thecompressed air stream being'directed onto the coupling coil to cool thatcoil also. As arranged for use heretofore, the oscillator was coupled tothe transformer of the heating unit independently of the cooling airstream. The disadvantage of such an arrangement is that, as long asenergy is being supplied to the transformer and the coupling coil by theoscillator, heat will be developed therein and, unless removed, the heatdeveloped may become excessive.

The primary object of my present invention is to provide an improvedheating device of the type set forth above which will not be subject tothe aforementioned disadvantage.

-More particularly, it is the object of my present invention to providean improved. heating system of the type set forth wherein energy will besupplied to the coupling coil by the oscillator only when the air treamis flowing;

Another object of my present invention is to provide, in a heatingsystem as above set forth, a singlecontrol device for both theoscillator and the compressed air source.

It is also an object of my present invention to provide, in a heatingsystem of the type set forth, simplifled control means for theoscillator.

. A further object of my present invention is to provide an improvedheating system as afore- 30 transformer to become closed.

said wherein the supply of cooling air will be conserved.

Another object of my present invention is to provide an improved heatingsystem of the type set forth which is simple in construction and highlyefficient in use.

In accordance wth my present invention, I employ a vacuum tubeoscillator having a plate transformer coupled to the plates or outputelectrodes of the vacuum tubes, a relay operated 15 is connected to thesupply line of the compressed air stream in such a way that, when thecompressed air is flowing toward the cooling coil, the last named switchwill be open, and when the compressed air stream has stopped flowing,the

last named switch will close. The system is arranged in such'a mannerthat normally when connected to a source of power, the relay isenergized to open the switch in circuit with the primary winding of theplate transformer. When,

however, a suitable valve device under control of the operator is openedto permit the flow of "the cooling air, the pressure responsive switchopens, thereby de-energizing the relay and permitting the switch incircuit with the plate Immediately, therefore, energy issupplied by theoscillator to the heating unit. Upon release of the valve by theoperator, the pressure responsive, control switch closes again as soonas the compressed air stops flowing, thereby once more energizing therelay which opens the transformer switch. Thus, the supply of energyfrom the oscillator to the heating unit is cut oil.

The novel features that I consider character- 4 istic of my inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional ob jects and advantages thereof, will best beunderstood from the following description of one invention.

Referring more particularly to the drawing, there is shown a supportingtube I of insulating material on which is wound the primary winding 3 ofa transformer coupled to a suitable high 66 frequency oscillator l by asuitable concentric cable represented in the drawing by the leads 1.Surrounding the primary winding 3 and spaced therefrom is a single-turnsecondary winding 3 to which is connected a frusto-conical-coupling collconstituting an inductor tip for heating the work, such as a rivet II,as mor 'fully described in my aforementioned patent.

To effect proper cooling of the windings 3 and 3 and also the inductortip N, there is formed on the end of the secondary winding 3 adjacent tothe inductor tip H a radially inwardly directed tubular member l3through which extends, radially in an outward direction, the nozzle endof a hose |1, through which compressed alr may be passed. Thisconstruction is also disclosed in greater detail in my aforementionedpatent and it is not believed to require any further description at thispoint.

The hose I1 is connected through a valve l3, a second hose 2|, a Tconnection 23, and a flexible coupling 25, to a compressed air pump orblower 21 having a motor connected to a suitable power source through amaster switch 23 and leads 30. The valve I3 is controlled through alever 3| carried by a handle 33 which is secured to the transformerwinding 3. When the lever 3| is drawn toward the handle 33, the valve I3is opened and the compressed air from the compressor 21 is directed tothe inductor tip When the lever 3| is released, the valve i9 is closedand the flow of the compressed air stream is out Off.

The oscillation generator includes one or more vacuum tube oscillators33 to the plates or output electrodes of which is connected atransformer 31. The filaments of the tubes 35 are connected to thesupply means or power source through a transformer 33, a pair of leads39 and the master switch 23, the transformer 31 being also connected tothe supply means through the switch 23, a portion of one lead 33, a lead4|, a lead 42, a relay operated switch 43, a lead 44, and a lead 45. Thecoil or winding 41 of the relay which controls the switch 43 isconnected in series with a control switch 43 having a fixed terminal 3|on a casing 33 which has air-tight connection with the T coupling 23 anda movable contact 55 connected by a flexible lead 31 to the lead 45. Themovable contact 55 is carried by a ilexible membrane or diaphragm 33 ofinsulating material and having an inherent bias such as to normallymaintain the contact 55 in engagement with the contact 5|. Within thevertical head of the T coupling 23 is a tube 63 so arranged that itsmouth or open end is opposite the adjacent end of the horizontal arm 23aof the T coupling 23. Thus, as the air stream flows through the tube 33,there is created in the arm 23a and in the portion of the casing 53 toth left of the diaphragm 59 a suction or decrease in pressure againstthe diaphragm 33) which causes the diaphragm to flex from the solid lineposition to the dotted line position, whereby to open the switchcontacts 33 and 3|. When, however, the valve I3 is closed. the diaphragm33 is restored to the normal, solid line position and the switch 43 isclosed again.

When the system is set up for operation, the master switch 23 is closedand energy is supplied to the filaments of the oscillator tubes 33through the leads 33, the filaments thereafter being maintainedconstantly hot. Closing of the switch 23 also supplies energy to theblower motor through the leads 30. At the same time, since the controlswitch 43 is closed, the relay coil 41 is energized to open the switch43. This breaks the circuit of the plate transformer 31 and. therefor nocurrent will flow in the output circuit of the oscillator to the primarywinding 3 of the heating transformer. Thus, there is no danger of theheating transformer or the inductor tip being heated. It will be notedthat, at this time, the

valve I3 is closed and no compressed air is flowing to the inductor tipor coupling coil |l. Now, when the lever 3| is depressed to open thevalve l3, compressed air from the compressor 21 immediately flowsthrough the hose H to the inductor tip The suction thus created to theleft of the diaphragm 33 causes th diaphragm to flex to the dotted lineposition, thereby disconnecting the switch contacts 33 and 3| to openthe. control switch 43 and break the circuit through the relay coil 41.A spring 3| then pulls the armature of the relay into position to closethe. switch 43, whereby the transformer 31 becomes energized and theoscillator immediately supplies energy to the heating transformer andthe coupling coil ll. As soon, however, as the lever 3| is released, theflow of compressed air is shut off and the change in velocity of thecompressed air eifects return of the diaphragm 33 to its solid lineposition to close the switch 43. The relay coil 41 is thus once againenergized to open the/switch 43 and the oscillator once more becomesinoperative to supply energy to the heating transformer.

From the foregoing description, it will be apparent to those skilled inthe art that I have provided a novel and simple control of theoscillator in accordance with whether or not cooling air is beingsupplied to the inductor tip or coupling coil. Although I have shown anddescribed but one embodiment of my invention, it will be apparent tothose skilled in the art that many changes in the particularmodification described, as well as other embodiments of the invention,are possible. I therefore desire that my invention shall not be limitedexcept insofar as is made necessary by the prior art and by the spiritof the appended claims.

I claim as my invention:

1. In an electrical heating system for heating work by induction, thecombination of a supporting device, a coupling coil adapted to beapplied to the work for inducing heating current therein, said coilbeing carried by said supporting device, means for supplying electricalenergy to said coil, means for directing a stream of cooling fluid tosaid coil, manually operable means also carried by said supportingdevice for controlling the flow of said stream, and means responsive toa change in flow of said stream for controlling the supply of energy tosaid coil by said first named means.

2. In an electrical heating system for heating work by induction, thecombination of a supporting device, a coupling coil adapted to beapplied to the work for inducing heating current therein,

- said coil being carried by said supporting device,

means for supplying electrical energy to said coil, means for directinga stream oi cooling fluid to said coil, manually operable means alsocarried by said supporting device for controlling the rate of flow ofsaid fluid, and means responsive to a change in the rate of flow of saidfluid for controlling the supply of energy to said coil y said firstnamed means.

3. In an electrical heating system for heating work by induction, thecombination of a supporting device, a coupling coil adapted to beapplied to the work for inducing heating current therein,

said coil being carried by said supporting device, means for supplyingelectrical energyto said coil, means associated with said first namedmeans for controlling the supply of energy to said coil, said secondnamed means including a control member operable in response to change inpressure, means for directing a stream of cooling fluid to said coil,manually operable means also carried by said supporting device forcontrolling the velocity of said stream, and means associated with saidmemher and said stream for converting changes in velocity of said streaminto changes of pressure cn said member whereby to operate said memberto control the supply of energy to said coil.'

-4. In an electrical heating system for heating ,york by induction, thecombination of a supporting device, a coupling coil adapted to beapplied to the work for inducing heating current therein,

said coil being carried by said supporting device, a high frequencyoscillator coupled to said coil for supplying high frequency energythereto, a control switch associated with said oscillator forcontrolling the output thereof, means for directing a stream ,of coolingfluid to said coll, manually operable means also carried by saidsupporting device for controllin the flow of said cooling thereto, atransformer connected to the output electrodes of said vacuum tubes,means for directing a stream or cooling fluid to said coil, manuallyoperable means also carried by said supporting device for controllingthe flow of said cooling fluid to said coil, and means responsive to achange in flow of said stream resulting from operation of said manuallyoperable means for controlling the operativeness of said transformer.

6. In an electrical heating system for heating work by induction, thecombination Of a supporting device, a coupling coil adapted to beapplied to the work for inducing heating current therein. said coilbeing carried by said supporting device, a high frequency vacuum tubeoscillator coupled to said coil for supplying high frequency energythereto, a transformer connected to the output electrodes of said vacuumtubes, a switch in circult with said transformer, means for normallymaintaining said switch open whereby said oscillator is normallyincapable of supplying energy to said coil, means for directing a streamoi'cooling fluid to said coil, manually operable means also carried bysaid supporting device for controlling the flow of said cooling fluid tosaid coil. and control means responsive to the flow of said fluidresulting from operation of said manually HENDERSON C. GILLESPIE.

